Technical Field
The present invention relates to a measuring device and a tilt sensor which obtain a tilt of a rotational unit rotatably provided in a base unit.
Description of Related Art
For example, in surveying, three-dimensional coordinates of a target object are measured with a distance measuring device such as a total station. Such a measuring device includes an electro-optical distance meter rotatably provided inside a base unit to emit light to a target object, receive reflected light thereby and measure a distance to the target object. The measuring device is required to detect a tilt angle and direction of the rotational axis of a rotational unit of the distance meter relative to a horizontal plane with high precision for precisely finding the three-dimensional coordinates of the target object. Japanese Laid-open Patent Application Publication No. 2007-127628 (Reference), for example, discloses a measuring device which uses a tilt sensor to detect a tilt relative to the horizontal plane by use of a fluid free surface maintaining a level state by gravity. This tilt sensor is provided in the rotational unit of a distance meter so that it is able to detect a tilt of the rotational axis relative to the horizontal plane precisely.
However, there is a problem in the measuring device that since the distance meter is provided in the rotational unit and the fluid free surface in the tilt sensor moves along with the rotation of the rotational unit, it is difficult to precisely detect the tilt of the rotational axis of the distance meter. Thus, there is a room for improvement of the measuring device composed of a base unit and a rotational unit using a fluid free surface in terms of precisely detecting a tilt of the rotational axis of a rotational unit relative to a horizontal plane.